Contact lenses for myopic eyes and methods of treating myopia

ABSTRACT

A contact lens and a method for treating an eye with myopia is described. The contact lens includes an inner optic zone and an outer optic zone. The outer optic zone includes at least a portion with a first power, selected to correct distance vision. The inner optic zone has a relatively more positive power (an add power). In some embodiments the add power is substantially constant across the inner optic zone. In other embodiments the add power is variable across the inner optic zone. While in some embodiments the inner optic zone has a power designed to substantially eliminate lag of accommodation in the eye with myopia, in other embodiments, the add power may be higher.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application is a United State National Stage Application filedunder 35 U.S.C. §371 of PCT Patent Application Ser. No.PCT/AU2011/000235 filed on Mar. 3, 2011, which claims the benefit of andpriority to Australian Patent Application No. 2010900904 filed on Mar.3, 2010, both of which are hereby incorporated by reference in theirentireties.

FIELD OF THE INVENTION

The field of the invention is contact lenses for myopic eyes and methodsof treating myopia. In particular, the contact lenses of the inventionand associated methods are applicable to myopic eyes that are not alsosubstantially presbyopic. Embodiments of the invention are applicable tomyopic eyes in which the myopia is progressing.

BACKGROUND OF THE INVENTION

Many people suffer from myopia (short-sightedness). The prevalence ofmyopia is increasing, leading to increased attention to the developmentof solutions. In addition, for many people, myopia progresses over time,despite correction using some existing methods.

FIG. 1 shows an eye that is normal sighted (i.e. is neither long-sightednor short-sighted). FIG. 2 shows a myopic eye viewing a distant object;the focal point of the image is located in front of the retina. Thisshifted focal point relative to the retina creates blur.

Several techniques have been used to correct myopia. These techniquesinclude prescribing spectacle lenses or contact lenses or intra-ocularlenses, surgical reshaping of the cornea and temporary reshaping of thecornea by hard or soft contact lenses.

When looking at near objects, it has been observed that many individualswith myopia accommodate less than that which is needed to bring theimage forward onto the retina. This under-accommodation is oftenreferred to as a lag of accommodation. FIG. 3 shows a myopic eye with alag of accommodation; the focal point of the image is located behind theretina. Studies involving children indicate that lag of accommodationtypically increases with increasing near focus (i.e. accommodation)demand. In a study involving children of primarily European descent, lagof accommodation measured at 33 centimetres using an autorefractor foundthe median lag to be 1.26 D (range from −0.75 to 2.82 D) in childrenaged 8 to 11 yrs. In children of Chinese ethnicity, lag of accommodationmeasured at 33 centimetres was 0.74+1-0.27 D.

Patent publication EP 2004/005560 A1 to Radhakrishnan et al describes amethod said to retard or control the progression of myopia bycontrolling aberrations, thereby manipulating the position of the mediumand high spatial frequency peaks of a visual image in a predeterminedfashion. The repositioning of medium and high spatial frequency peaksintending to alter accommodative lag. The method calls for providing anocular system of a predetermined aberration controlled design and forthe design to provide negative spherical aberration.

International patent publication WO 05/055891 A1 describes the use of acontact lens to control the relative curvature of field with anobjective of controlling the progression of myopia. The method includesmoving peripheral images forwards relative to the retina, while allowingclear central vision.

U.S. Pat. No. 6,752,499 (Aller) describes the use of multifocal contactlenses to control the progression of myopia in myopic eyes withesofixation disparity. Aller describes providing a lens that providesfor acceptable distance visual acuity and reduces or corrects esophoriaat near. Aller describes use of near centre bifocal lenses having an addpower of up to 2.25 D and the use of distance centre lenses with addpowers of up to 2.5 D.

Multifocal and bifocal contact lenses have also been designed forpresbyopic eyes.

U.S. Pat. No. 6,457,826 (Lett) describes a centre near bifocal lens anda centre distance bifocal lens. A described embodiment of a centre nearbifocal lens has a constant power centre area extending to a chorddiameter of 2.07 mm, a distance power outer area commencing at a chorddiameter of 2.71 mm and a gradient power aspheric area that provides acontinuous power transition from the centre area to the outer area. Fora 3.0 mm pupil, Lett says that the near power occupies 48% of the pupilarea and the distance power 18%. For a 5.0 mm pupil Lett says that thenear power occupies 17% of the pupil and the distance power 71%.

U.S. Pat. No. 5,139,325 (Oksman et al) describes a lens with a visioncorrection power that is inversely proportional to the radial distanceof the lens. In a described example, a lens has an add power overdistance vision of 2.75 diopters centrally up to a radius of 0.72 mm,with the add power decreasing inversely proportional with radius after0.72 mm. Another example has an add power over distance vision of 3.00diopters up to a radius of 0.66 mm. The add power is described as notreaching zero unless the function is truncated.

U.S. Pat. No. 5,754,270 (Rehse et al) describes a lens with a centralaspheric zone with an add power over distance vision of between 2.25 to2.50 D up to a diameter of about 2.4 mm, a change in add power of about0.5 to 1.25 D over the area between the diameters of 2.4 mm and 2.5 mmand then a progressive reduction in add power down to the power requiredfor distance vision correction at about 6 mm diameter.

Reference to any prior art in the specification is not, and should notbe taken as, an acknowledgment or any form of suggestion that this priorart forms part of the common general knowledge in any jurisdiction orthat this prior art could reasonably be expected to be ascertained,understood and regarded as relevant by a person skilled in the art.

SUMMARY OF THE INVENTION

The invention generally relates to a contact lens and to the use of acontact lens for treating an eye with myopia.

The contact lens includes an inner optic zone and an outer optic zone.The outer optic zone includes at least a portion with a first power,selected to correct distance vision. The inner optic zone has arelatively more positive power (an add power). In some embodiments theadd power is substantially constant across the inner optic zone. Inother embodiments the add power is variable across the inner optic zone.While in some embodiments the inner optic zone has a power designed tosubstantially eliminate lag of accommodation in the eye with myopia, inother embodiments, the add power may be higher, for example up to about4 diopters.

The reference to correction of distance vision includes providing a lenswith a first power that substantially eliminates blur.

In some embodiments, the outer optic zone includes at least a portionwith a third power, relatively more positive in power than the firstpower. The portion with a third power is distinct from the inner opticzone; the third power is separated from the inner optic zone by aportion having the first power. The third power may be substantiallyequal to the add power if the add power is constant or the third powermay be substantially equal to the maximum add power in the inner opticzone if the add power is variable. Alternatively, the third power may bedifferent to the second power. In some embodiments the third power isrelatively more positive than the add power.

In some embodiments, the outer optic zone includes at least'two portionswith relatively positive power compared to the first power, separated bya portion with the first power. In some embodiments, each of said at,least two portions have the same power. Alternatively, each of said atleast two portions have different powers. When the powers differ, theportion with relatively more positive power may be located on thecontact lens at a greater radial distance than the portion withrelatively less power.

In some embodiments, the diameter of the inner optic zone and/or otheradd power portions of the lens is/are selected to be a maximum whilestill maintaining acceptable distance vision. The selection may be aniterative process, taking into account progression of myopia and theeffect on distance vision of the portions of the lens with add power.

In some embodiments, the inner optic zone comprises a meridian extendingacross the optic zone.

In some embodiments, the inner optic zone is located off-set from thecentre of the contact lens. In these embodiments the contact lens isstructured to adopt an orientation when fitted to the eye so that theinner optic zone is located off-set from the centre in the nasaldirection.

In some embodiments, any zone that acts to correct for the refractiveerror of the eye for distance may correct the refractive error toprovide substantially clear distance vision.

A method of providing a contact lens for a myopic eye includes providinga lens as described above with a proportion having a power to correctdistance vision and a proportion having an add power. The proportionsand/or the power profile and/or the magnitude of the add power is thenvaried with an objective of influencing the rate of myopia progressionand/or an objective of maintaining acceptable distance vision.

A range of contact lenses may be provided to allow selection of a lenswith varied characteristics as described above, without having to custommanufacture a lens for an individual recipient.

Further general aspects of the invention and further embodiments of theaspects described in the preceding paragraphs will become apparent fromthe following description and/or from the accompanying figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1: shows an eye that is normal sighted.

FIG. 2: shows a myopic eye viewing a distant object.

FIG. 3: shows a myopic eye with lag of accommodation.

FIG. 4: shows a plan view of an embodiment of a contact lens of thepresent invention.

FIG. 5: shows a cross-section through the contact lens of FIG. 4.

FIG. 6: shows a myopic eye viewing distant objects through the contactlens of FIG. 4.

FIG. 7: shows a myopic eye viewing near objects through the contact lensof FIG. 4.

FIG. 8: shows a plot of relative power against radius for severalembodiments of lens according to the present invention.

FIG. 9: shows a treatment profile for myopia of increased relativecurvature of field.

FIG. 10: shows a plan view of another, embodiment of a contact lens ofthe present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

1. Introduction

As discussed briefly above, myopic eyes may experience a lag ofaccommodation when viewing near objects. Larger lags of accommodationmay be associated with progression of myopia. Due to the lag, it ispossible that when reading near texts or objects, the retina is exposedto blur or defocus (hyperopic). This blur or defocus has been theorisedto act as a stimulus to eye growth.

One mechanism by which the accommodative error can be reduced is withthe use of a plus lens (a lens with positive power relative to thedistance power of the lens) during near viewing. The positive powerserves to bring the image closer to the 1.5 retina, thus reducing oreliminating the lag of accommodation. Bifocal spectacles or multifocalspectacles such as progressive addition lenses (superior zone of thelens providing for distance vision and the inferior zone carryingpositive power relative to the distance zone to provide for nearviewing) may be used to provide such additional positive power for nearviewing.

An issue with the use of spectacle lenses is compliance whilst viewingat near objects. For the lens to be effective, the lower portion of thelens with added positive power should be used whilst looking at nearobjects. However, as there is no incentive to direct gaze through thelower portion of the spectacle, the patient, particularly children, maytilt their head down whilst looking at near objects and continue to usethe distance portion of the lens, rather than the near portion.

In this situation, a contact lens provides for better compliance as itis aligned with the eye thus eliminating the need for eye versus headmovements. Also, in the spectacle wearing situation, even in instanceswhere the child directs gaze through the lower portion of the spectaclethe gaze shift and eye movements that occur behind the spectacle make itdifficult to align the appropriate power with the eye at all times.Given that the contact lens is placed on the front surface of the eyeand is completely aligned with the eye movements a contact lens that hasan appropriate power profile ensures that the child receives anappropriate corrective power at all viewing distances.

2. Contact Lenses with Zones of Different Power

FIG. 4 shows a plan view of an embodiment of a contact lens 100 for usein correcting myopia. The lens 100 includes three zones and a transitionzone. The three zones are an inner optic zone 1, an outer optic zone 2and a peripheral zone 3. A transition zone 4 is located between theinner optic zone 1 and the outer optic zone 2. All zones are within thelens's outer peripheral edge 5, which is represented as a dashed line inFIG. 4.

FIG. 5 shows a cross-section through the diameter of the lens 100. Inthe embodiment shown the lens 100 is rotationally symmetric. Manufactureof rotationally symmetric lenses may be simpler than asymmetric lenses.However, as explained below, some embodiments of lens are asymmetrical.The lens includes an anterior surface 6 and a posterior surface 7.

The lens 100 may be either a soft or a hard corneal contact lens. Forexample, the lens may be a silicone-hydrogel corneal contact lens or arigid gas permeable corneal contact lens. The lens 100 may alternativelybe a corneal on-lay, provided on the cornea, below the epithelium, whichmay for example have been scraped away and regrown over the lens. Wherethe lens is a rigid contact lens or a corneal on-lay, the peripheralzone 3 may be omitted.

2.1 Dimensions and Power of the Inner Optic Zone

The diameter D1 of the inner optic zone 1 approximates or is less thanthe pupil diameter P1 during viewing at near distances. P1 is typicallybetween 2 and 4 mm, depending on the recipient of the lens. The neardistance may correspond to the distance where there is more thannegligible or insubstantial of accommodation. The inner optic zone 1 maybe about 10% of P1, up to about 100% of P1. However, it is expected thatfor many lens recipients, an appropriate diameter D1 of the inner opticzone 1 will be selected from with the range of 50% to 100% of P1.

The power of the inner optic zone 1 is relatively more positive than therefractive power of the outer optic zone 2. The differential power ofthe inner optic zone 1 to the outer optic zone 2 may be selected fromwithin a range of approximately 0.5 D and 4.00 D. For example, if theouter optic zone 2 had a power of −1.50 D, then the inner optic zone mayhave a power from about −1.00 D to 2.50 D.

In some embodiments, the power of the inner optic zone 1 is selectedhaving regard to the lag of accommodation of the myopic eye when viewingat near distances. For example, the power may be selected tosubstantially reduce or to eliminate the lag of accommodation. The powermay then be selected to be substantially uniform across the inner opticzone 1. This approach may be particularly appropriate when the inneroptic zone 1 is larger (i.e. 50% of P1 or more). In other embodimentsthe power may vary across the inner optic zone 1, whether or not theinner optic zone is 50% of P1 or more and at least a portion of the addpower may be more than that required to correct lag of accommodation.

Embodiments where add power of the inner optic zone is more than thatrequired to correct the lag of accommodation may be particularlyappropriate where the inner optic zone 1 is less than 50% of P1.

The selection between a smaller or larger inner optic zone 1 may bebased on the pupil diameter of the recipient of the contact lens,subjective acceptance of the contact lens 100 and having regard to therequired proportion of plus power zones (see below).

In the embodiments described in this specification, the inner optic zone1 is shown as extending from the centre of the lens to a certaindiameter, so as to represent a solid disc when viewed from the anteriorsurface of the contact lens. The inner optic zone 1 could however haveanother shape, other than circular, although this may increase thecomplexity of manufacture.

2.2 Diameter and Power of the Outer Optic Zone

The outer optic zone 2 is annular, with an inner diameter equal to D1(when both zones are measured from a mid point in the transition zone 4)and an outer diameter D2. The outer diameter D2 approximates the pupildiameter P2 during viewing at distant objects. P2 is typically between 3and 8 mm, depending on the patient. In other embodiments the outer opticzone 2 may be larger than P2.

The outer optic zone 2 has a refractive power chosen having regard tothe myopic condition of the eye to which the contact lens 100 is to beapplied. For example, in many embodiments, it is expected that therefractive power will be chosen to give the eye substantially cleardistance vision. In some embodiments, the outer optic zone 2 has asubstantially constant power with increasing radius. In otherembodiments the outer optic zone 2 may include a plurality of sub-zoneswith different powers. In these other embodiments, a substantialproportion of the outer optic zone 2 is still allocated to correctingdistance vision of the myopic patient.

2.3 Selecting and Adjusting Contact Lens Design Parameters

The proportion of the lens occupied by the one or more zones of addpower relative to the distance correcting zones can be adjusted byadjusting any one or combination of the variables:

-   -   The size of the inner optic zone;    -   The power profile of the inner optic zone (e.g. whether it has        substantially uniform power across its radius, or whether there        is a plurality of powers across the radius, for example a smooth        aspheric function or a stepwise function);    -   The power profile of the outer optic zone.

In some embodiments approximately 40% to 50% of the entire field ofvision under normal indoor lighting conditions when the eye is viewing adistant object is allocated to correcting distance vision. In otherembodiments approximately 50% to 60% is allocated to correcting distancevision. In other embodiments at least 70% is allocated to correctingdistance vision.

A method, of treating myopia therefore includes an iterative process ofprescribing a lens with a first proportion allocated to distance visionand a second proportion allocated to one or more zones with relativelyplus power. The distance vision is then evaluated and the relativeproportion of distance vision correction zones and relative plus powerzones changed to reach or get closer to a required proportion of pluspower zones, while maintaining acceptable distance vision. The requiredproportion may be the maximum that still maintains acceptable distancevision.

For example, the method may include commencing with a lens with an inneroptic zone of diameter D1 substantially equal to the pupil diameter whenthe patient is viewing near objects in normal indoor light conditionsand a diameter D2 substantially equal to or greater than the pupildiameter P2 when the patient is viewing distant objects under the samelight conditions. The distance vision of the patient may then beevaluated. If the distance vision is acceptable, the proportion ofrelative plus power may optionally be increased, by increasing thediameter of the inner optic zone and/or providing a plus power sub-zonein the outer optic zone. The distance vision of the patient may then bere-evaluated and the proportion adjusted if necessary. This process ofincreasing the proportion of plus power with acceptable distance vision(which may include patient acceptance) as a criteria for limiting theproportion may be adopted, for example, if the patient's myopia isprogressing past a certain level and/or based on the lag ofaccommodation and/or based on the amount of defocus as determined at theperipheral retina. For example, the process may be adopted if thepatient is progressing more than 0.5 D per year more than 0.7 D or 0.8 Dper year. If the distance vision is not acceptable, the diameter of theinner optic zone may be decreased and/or any relative plus power zone inthe outer optic zone decreased in size or removed.

In addition to, or instead of varying the proportion of relative pluspower zones, the relative positive power of the plus power zones may bevaried, using a similar approach as described above (e.g. increasing thepower of the plus power zones until a limit of acceptable distancevision is reached, perhaps less a buffer). Also, as described above thepower profile may be changed, between constant and variable power acrossthe inner optic zone and between different rates and/or magnitudes ofchange within the inner optic zone.

The design of a lens for a patient may be made with reference to therate of myopia progression after an initial contact lens 100 has beenfitted for a period of time, for example 3 to 6 months or 12 months. Forexample, the practitioner may start with a lens with an inner optic zone1 of diameter D1 substantially equal to the pupil diameter with thepatient is viewing near objects in normal indoor light conditions and adiameter D2 substantially equal to or greater than the pupil diameter P2when the patient is viewing distant objects. The entirety of the outeroptic zone 2 is dedicated to distance vision correction. After theevaluation period has expired, the progression, if any, of myopia ismeasured and if this above a certain threshold, for example above anannual rate of 0.5 D (or in other embodiments more than 0.7 D or 0.8 Dper year or some other rate, which may be determined as being a requiredreduction in the rate of progression in comparison to before the contactlens 100 was fitted), then an increased proportion of the lens may bededicated to relative plus power and/or one or more plus power zones maybe given an increased relative positive power and/or the profile of theinner optic zone may be changed, for example from the general profile oflenses L1-L3 to the general profile of lenses L4-L6 (see descriptionbelow and FIG. 8).

The design of a lens for a patient is made in conjunction with theselection of the power of the lens. For instance, a practitioner mayselect the portion of the outer optic zone dedicated to distance visioncorrection to under correct the myopia, for example by about 0.5 D orabout 0.25 D. It has been theorised that for at least some patientsunder correction may assist in reducing the rate of progression ofmyopia.

For example, a practitioner may:

-   1. Identify the myopic correction required and adjust if required,    for example to under correct the myopia: this will set the power of    the outer optic zone 2;-   2. Identify the relative positive power required to focus the rays    from a near object to an image point closer to, on, or in front of    the retina: this will determine the power of the inner optic zone 1;-   3. Identify the power for any relative plus power subzones in the    outer optic zone 2, which may be initially selected to match the    power identify in step 2.-   4. Adjust the relative proportion of plus power zones to distance    correction zones as described above.

After the patient has worn the lens for a period of time, thepractitioner may:

-   5. Re-evaluate the vision of the patient and identify any correction    required to the relative power and/or relative proportion of plus    zones to distance correction zones;-   6. Prescribe a second lens with the adjusted power profile.

The practitioner may of course continue to monitor the patient andrepeat the steps described above periodically to maintain acceptablevision and in response to measured progression of myopia, if any.

Examples of the power profile are described below with reference to FIG.8 and it will be appreciated that each of these may be modified toachieve any required proportion of zones to distance correction andzones with relatively positive power.

2.4 The Transition Zone

The transition zone 4 between the inner optic zone 1 and the outer opticzone 2 blends the inner and outer optic zones, so as to provide acontinuous power profile. The transition zone 4 may be provided wherethere is a step wise change between the power of the peripheral part ofinner optic zone 1 and the power of the inner part of the outer opticzone 2. In other embodiments where the power across the inner optic zone1 and/or the outer optic zone 2 changes with diameter and bothintersect, no separately designed transition zone 4 is necessary (thetransition is an inherent part of the design). In some embodiments, thetransition zone may be narrow, so that the power profile effectivelyincludes a discontinuity.

2.5 The Peripheral Zone

The peripheral zone 3 is shaped to rest on the sclera of the eye andacts to locate and retain the contact lens 100 in place. As previouslymentioned, when the contact lens 100 is a corneal on-lay, the peripheralzone 3 may be omitted.

2.6 Effect of the Contact Lens

FIGS. 6 and 7 show a myopic eye viewing distant and near objects througha contact lens 100 of the type shown in FIGS. 4 and 5. In FIG. 7 thedashed lines show the path of light rays through the lens 100 and thesolid lines show light rays without the lens 100 for the purposes ofcomparison. In this example, the lens 100 has been designed so thatlight from a near object passing through the central optic zone isfocussed on the retina or in other words the inner optic zone 1 has beendesigned to eliminate the lag of accommodation by placing the image ofnear objects on the retina. FIGS. 6 and 7 only show light rays for theportion of the lens designed for the distance of their respectiveobjects. In particular: FIG. 6 only considers the light rays through theportion of the outer optic zone 2 that has been designed to correctdistance vision and not the ‘relatively positive powered inner opticzone 1; FIG. 7 only considers the light’ rays through the portion of theinner optic zone 1 that fully corrects the lag of accommodation.

2.7 Power Profile Embodiments and Misalignment of the Pupil Centre withthe Lens Centre

FIG. 8 shows a graph illustrating examples of possible power profilesacross the inner optic zone 1 and the outer optic zone 2, plottedagainst the radius of the lens. The graph has been drawn to show thepower differential of the lens relative to the power required to correctthe distance vision of a myopic patient. In FIG. 8, the relative powerdifference is plotted on the vertical axis with a unit of power indioptres (D) and the radial distance from the lens axis (or simplyradius) is plotted on the horizontal axis in millimetres. FIG. 8 showsthe profiles of six different multizone lenses L1-L6, where:

-   -   L1 has an inner zone 1 with a differential power of a maximum of        2 D that peaks at the centre (radius 0 mm). The outer optic zone        2 may be viewed as commencing anywhere between a radius of about        0.5 to 1.0 mm; the two zones combine to form a continuous and        relatively smooth power profile. The outer optic zone 2 includes        two sub-zones: an inner sub-zone having a substantially constant        power selected to correct distance vision; and an outer sub-zone        with positive power differential, commencing at about a radius        of 2.25 mm.    -   L2 Has a similar power differential profile to the lens L1,        except the outer optic zone 2 is entirely dedicated to        correcting distance vision.    -   L3 Has a similar power differential profile to the lens L2, but        with a larger diameter inner zone 1 and a slower rate of change        across the inner zone 1.    -   L4 Has an alternative near and distance ‘ring’ structure,        including a positive power inner zone 1 of 2 D more positive        power than the power required to correct distance vision. The        outer optic zone 2 commences at a radius of about 1 mm. The        outer optic zone 2 includes 3 sub-zones: a ring at the power to        correct distance vision; a positive power ring of 2 D more        positive power than the power required to correct distance        vision between a radius of 1.5 mm to about 1.9 mm; and then        another ring to correct distance vision. In other embodiments        more rings may be provided, alternating between the power for        distance correction and a relative positive power. Each ring of        relative positive power may have the same power as each other        ring, or the power of the rings may differ.    -   L5 Has an inner zone 1 of substantially constant power and which        is about 2.0 mm in diameter. A narrow transition zone 4 is        provided to an outer optic zone 2 and the differential power        between the zones is 3 D.    -   L6 This lens provides a larger diameter inner zone 1 and a        transition zone 4 located generally between a radius of 1.0 mm        and 1.75 mm. The outer optic zone 2 has a constant power with        radius.    -   L7 This lens provides an inner zone 1 with relatively constant        power of about 1.5 D more positive than the distance vision        correction. The inner zone diameter is about 2 mm (1 mm radial        distance from axis). The outer optic zone is divided into an        inner sub-zone between about 1 mm and 2 mm radial distance and        an outer sub-zone beginning at about 2 mm radius. The inner        sub-zone provides a constant power for correction of distance        refractive error while the outer sub-zone repositions the        peripheral image points forward by providing increasing (up to        +1.5 D) peripheral power.

A lens of a configuration like lens L1 may account for possiblemisalignment of the pupil centre with the lens centre by still providingadequate power at all distances.

For example, if the pupil centre is decentred by 1.0 mm, then when thewearer is looking at near objects the inner optic zone 1 will not beeffective to provide adequate positive power. The outer sub-zone of theouter optic zone therefore provides the required difference, or at leastreduces the shortfall. The positive power ring in lens L4 may also dealwith misalignment of the pupil centre with the lens centre in a similarway and other embodiments of lens may include two or more positive powersub-zones that assist with near vision when the lens is not aligned withthe pupil.

2.8 Rotationally Symmetric and Asymmetric Embodiments

While the foregoing description has predominantly focussed onrotationally symmetric lenses, other lens configurations may be used.For example, instead of a generally circular inner optical zone 1(viewed from along the central/optic axis of the lens), the inneroptical zone 1 may be a meridian extending across the lens. The meridianmay be 0.5 to 3 mm wide, matching the diameter of the inner optical zone1 described previously. The meridian may terminate at the peripheralzone 3. In this embodiment, the outer optical zone 2 would be twomeridians, one on each side of the inner optic zone 1. FIG. 10 shows thegeneral structure of a lens 50 of this configuration with a meridianinner optic zone 51, a first meridian outer optic zone 52, a secondmeridian outer optic zone 53 and a peripheral zone 54. As with the lensstructure shown in FIGS. 3 and 4, the peripheral zone 54 may be omittedfor a hard contact lens or corneal on-lay. The power profile along avertical half-meridian (with reference to the orientation of the lens 50shown in FIG. 10) may be any of the profiles described above withreference to FIG. 8.

If a lens is ballasted or otherwise formed to orient on the eye andremains in position when the eye moves, then the inner optical zone 1may be located off-centre. This location may reflect the inward movement(towards the nose) of the pupil when viewing near objects. This movementmay be about 0.5 mm.

3. Peripheral Treatment Profile

In some embodiments, the contact lens 100 is designed to provide aperipheral treatment profile.

3.1 A Peripheral Treatment Profile for Myopia

A form of peripheral treatment profile for myopia is increased relativecurvature of field. The lens is designed so that images coming to afocus at the peripheral retina are shifted forwards so that they come toa focus to onto or in front of the retina. The use of a contact lens tocontrol the relative curvature of field to this end is described ininternational patent publication WO 05/055891 A1, the content of whichis incorporated herein in its entirety. FIG. 9, which is a reproductionof FIG. 3a of WO 05/055891 A1 shows the manipulation of peripheralimages, by the moving forward of the focal point in front of the retina.

3.2 Example Lenses that May Provide a Peripheral Treatment Profile

The lens L1 represented in FIG. 8 may provide a peripheral treatmentprofile for myopia. As previously discussed, in addition to therelatively positive power inner optic zone 1, the lens L1 has an outeroptic zone 2 including an outer sub-zone with positive powerdifferential, commencing at about a radius of 2.25 mm. Both the inneroptic zone 1 and the outer sub-zone act to move peripheral imagesforwards. However, increased freedom of design to place peripheralimages on or in front of the retina may be available with the outersub-zone, since the inner sub-zone may be constrained by the requirementto provide clear vision at near distances.

The ‘ring’ design lens L4 represented in FIG. 8 may also provide aperipheral treatment profile for myopia. In this lens the ringcommencing at a radius of 1.5 mm acts to shift peripheral imagesforwards. In other embodiments, several rings may be present, each ofwhich move peripheral images onto or in front of the retina. The ringsmay be constant width or alternatively may change in width, for examplewith the outer rings being wider than the inner rings.

As discussed above, the relatively positive power sub-zones within theouter optic zone 2 may be useful in dealing with possible misalignmentof the contact lens 1 with the pupil. In some embodiments, the relativepositive power sub-zones may have a power selected to match thatrequired to clearly focus near images. The practitioner may checkwhether this also places peripheral images through that part of the lenson or in front of the retina. If not, the power may be increased toachieve this objective. Alternatively, the practitioner may design therelative positive power subzones of the outer optic zone 2 with theobjective of peripheral image control, substantially without regard tothe power required to clearly view near objects. Where there are two ormore relative positive power subzones, an inner positive power subzonemay have a power that takes account of near object vision requirementsand an outer subzone may have a power designed with reference toperipheral image control, for instance by having a power differentialhigher than that required to correct the lag of accommodation of theeye.

A practitioner may start by prescribing a lens with a power profile witha lesser area with relative positive power and then progress to lenseswith increased areas of relative positive power if myopia progression isstill an issue. For example, a practitioner may start by prescribing alens that has an inner optic zone 1 with reduced diameter relative tothe pupil diameter when viewing near objects and the entire outer opticzone dedicated to distance vision. If myopia is still progressing, thepractitioner may increase the area of the inner optic zone 1 toapproximate the pupil diameter. Next the practitioner may add a relativepositive power sub-zone to the outer optic zone and may continue toincrease the area of relative positive power sub-zones until either themyopia progression is halted or an unacceptable level of distance visionis reached.

As previously mentioned, different combinations of lenses may be formed,for example by combining the lens L1 with one of lenses 4 to 6 tocontrol the position of peripheral images.

The location and shape of the relatively positive power sub-zones may beselected to avoid any image priority zones that are in or extend intothe outer optic zone 2. The combination of image priority zones withperipheral image aberration is described in international patentpublication WO 2007/082268 A2, the content of which is incorporatedherein it its entirety. For example, referring to FIG. 8, a lens mayhave a power profile of the general shape of L1 along most halfmeridians, but have a power profile of the general shape of L2 along onehalf meridian, that half meridian having a width of between 0.5 mm to 3mm.

It will be understood that the invention disclosed and defined in thisspecification extends to all alternative combinations of two or more ofthe individual features mentioned or evident from the text or drawings.All of these different combinations constitute various alternativeaspects of the invention.

The invention claimed is:
 1. A contact lens for myopia, the contact lenscomprising an inner lag reduction optic zone with a diameter in therange of 1 to 2 mm, a transition zone and an outer myopia correctionoptic zone surrounding the transition zone, the outer myopia correctionoptic zone having at least a portion immediately adjacent saidtransition zone with negative power that corrects myopia of the eye of awearer, wherein the inner lag reduction optic zone is such as to reduceor eliminate lag of accommodation by said eye when viewing at neardistances, said inner lag reduction optic zone having an add powerportion with a substantially constant add power relative to the saidnegative power of between 0.5 diopters and 4 diopters inclusive, andwherein the transition zone occupies a radial distance of 0.5 mm orless.
 2. The contact lens of claim 1, wherein the outer myopiacorrection optic zone includes at least a portion with a third power,relatively more positive than said negative power, wherein the portionwith a third power is distinct from the inner lag reduction optic zone.3. The contact lens of claim 2, wherein the third power is substantiallyequal to the power in the add power portion.
 4. The contact lens ofclaim 2, wherein the third power is different to the power in the addpower portion.
 5. The contact lens of claim 4, wherein the third poweris greater than the power in the add power portion.
 6. The contact lensof claim 1, wherein the outer myopia correction optic zone includes atleast two portions with power greater than the power in the add powerportion, separated by a portion with the first power.
 7. The contactlens of claim 6, wherein each of said at least two portions have thesame power.
 8. The contact lens of claim 6, wherein each of said atleast two portions have different powers.
 9. The contact lens of claim8, wherein the portion with more positive power is located on thecontact lens at a greater radial distance than the portion with a lesserpower.
 10. A contact lens for myopia, the contact lens comprising aninner lag reduction optic zone and an outer myopia correction optic zoneimmediately surrounding the inner lag reduction optic zone, the outermyopia correction optic zone having at least a portion with negativepower and the inner lag reduction optic zone is such as to reduce oreliminate lag of accommodation by said eye when viewing at neardistances, said inner lag reduction optic zone including a centralportion with an add power relative to said negative power of between 1.5diopters and 4 diopters inclusive, wherein the inner lag reduction opticzone has a diameter of between 1 and 4 mm, and wherein the add power ofthe inner lag reduction optic zone progressively reduces with anincrease in diameter and wherein the power profile of the inner lagreduction optic zone equals the power of the outer myopia correctionoptic zone at the intersection of the inner lag reduction optic zonewith the outer myopia correction optic zone.
 11. The contact lens ofclaim 10 wherein the outer myopia correction optic zone has asubstantially constant negative power with radius.
 12. The contact lensof claim 10 wherein the central portion has an add power relative to thenegative power of between 2.6 diopters and 4 diopters inclusive.
 13. Acontact lens for myopia, the contact lens comprising an inner lagreduction optic zone and an outer myopia correction optic zoneimmediately surrounding the inner lag reduction optic zone, the outermyopia correction optic zone having at least a portion with negativepower and having a substantially constant negative power with radius,and the inner lag reduction optic zone is such as to reduce or eliminatelag of accommodation by said eye when viewing at near distances, saidinner lag reduction optic zone including a central portion with an addpower relative to said negative power of between 1.5 diopters and 4diopters inclusive, wherein the inner lag reduction optic zone has adiameter of between 1 and 4 mm.
 14. A contact lens for myopia, thecontact lens comprising an inner lag reduction optic zone and an outermyopia correction optic zone immediately surrounding the inner lagreduction optic zone, the outer myopia correction optic zone having atleast a portion with negative power and the inner lag reduction opticzone is such as to reduce or eliminate lag of accommodation by said eyewhen viewing at near distances, said inner lag reduction optic zoneincluding a central portion with an add power relative to said negativepower of between 1.5 diopters and 4 diopters inclusive, wherein theinner lag reduction optic zone has a diameter of between 1 and 4 mm, andwherein the central portion has an add power relative to the negativepower of between 2.6 diopters and 4 diopters inclusive.
 15. A method oftreating myopia in an eye with lag of accommodation, the methodcomprising providing a contact lens for the eye with an inner optic zoneand an outer optic zone, the inner optic zone correcting for the lag ofaccommodation and the outer optic zone correcting distance vision,wherein the inner optic zone is selected to be approximately the samediameter as the pupil of the eye when viewing near objects.
 16. A methodof treating myopia in an eye with lag of accommodation, the methodcomprising providing a contact lens for the eye with an inner optic zoneand an outer optic zone, the inner optic zone correcting for the lag ofaccommodation and the outer optic zone correcting distance vision,wherein the diameter of the inner optic zone is selected to be less thandiameter of the pupil of the eye to which it is to be applied whenviewing near objects.
 17. A method of treating myopia in an eye with lagof accommodation, the method comprising providing a contact lens for theeye with an inner optic zone and an outer optic zone, the inner opticzone correcting for the lag of accommodation and the outer optic zonecorrecting distance vision, wherein the diameter of the inner optic zoneis selected to be greater than diameter of the pupil of the eye to whichit is to be applied when viewing near objects.
 18. A method of treatingmyopia in an eye with lag of accommodation, the method comprisingproviding a contact lens for the eye with an inner optic zone and anouter optic zone, the inner optic zone correcting for the lag ofaccommodation and the outer optic zone correcting distance vision,wherein the outer optic zone has a substantially constant negative poweracross its entire radius.
 19. A method of treating myopia in an eye withlag of accommodation, the method comprising providing a contact lens forthe eye with an inner optic zone and an outer optic zone, the inneroptic zone correcting for the lag of accommodation and the outer opticzone correcting distance vision, wherein the outer optic zone includes aplurality of sub-zones, wherein a first sub-zone has a power selected tocorrect distance vision and a second sub-zone has positive powerrelative to the first sub-zone.
 20. The method of claim 19, wherein thesecond sub-zone is designed so that images at the peripheral retina arebrought to a focus one of closer to, on, or in front of the retina. 21.A contact lens for treating an eye with myopia, the contact lenscomprising an optic zone including an inner optic zone and an outeroptic zone, the outer optic zone including at least a portion with afirst power, that acts to correct distance vision of the eye and theinner optic zone including at least a portion with a second power,relatively positive than the first power, wherein the inner optic zonecomprises a meridian extending across the optic zone.